feat: add Reject approval policy with granular prompt rejection controls (#12087)
## Why
We need a way to auto-reject specific approval prompt categories without
switching all approvals off.
The goal is to let users independently control:
- sandbox escalation approvals,
- execpolicy `prompt` rule approvals,
- MCP elicitation prompts.
## What changed
- Added a new primary approval mode in `protocol/src/protocol.rs`:
```rust
pub enum AskForApproval {
// ...
Reject(RejectConfig),
// ...
}
pub struct RejectConfig {
pub sandbox_approval: bool,
pub rules: bool,
pub mcp_elicitations: bool,
}
```
- Wired `RejectConfig` semantics through approval paths in `core`:
- `core/src/exec_policy.rs`
- rejects rule-driven prompts when `rules = true`
- rejects sandbox/escalation prompts when `sandbox_approval = true`
- preserves rule priority when both rule and sandbox prompt conditions
are present
- `core/src/tools/sandboxing.rs`
- applies `sandbox_approval` to default exec approval decisions and
sandbox-failure retry gating
- `core/src/safety.rs`
- keeps `Reject { all false }` behavior aligned with `OnRequest` for
patch safety
- rejects out-of-root patch approvals when `sandbox_approval = true`
- `core/src/mcp_connection_manager.rs`
- auto-declines MCP elicitations when `mcp_elicitations = true`
- Ensured approval policy used by MCP elicitation flow stays in sync
with constrained session policy updates.
- Updated app-server v2 conversions and generated schema/TypeScript
artifacts for the new `Reject` shape.
## Verification
Added focused unit coverage for the new behavior in:
- `core/src/exec_policy.rs`
- `core/src/tools/sandboxing.rs`
- `core/src/mcp_connection_manager.rs`
- `core/src/safety.rs`
- `core/src/tools/runtimes/apply_patch.rs`
Key cases covered include rule-vs-sandbox prompt precedence, MCP
auto-decline behavior, and patch/sandbox retry behavior under
`RejectConfig`.
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